Choosing a charger that can equalize

[gardner]

I have a weekly-use off-grid cottage. I have nominally 235Ah @ 12V that I need to charge and equalize occasionally from a 6kW generator.
Mostly, generator charging can be through a 1000W/20A inverter-charger, however this is at a slow C/12 rate and the inverter/charger doesn't handle equalization at all.

I'm seeking advise on choosing a separate charger that could do a three-stage charge at ~40A and that can do equalization. Most of the units I find online do not do equalization. Is there a go-to charger that folks recommend in this range?

[Mike90250]

I have a Vector VEC1093 Smart Battery Charger (2/10/20/40/100 Amp) that can maintain 40A for hours, and it does EQ . I got mine from Amazon, also sold under the Black&Decker brand.

I've used it so much, that I had to replace the fan once.

[gardner]

Thanks Mike, that would be perfect. But it looks like they've discontinued it. I'll snoop around to see if I can find a NOS somewhere.

All the current inexpensive models I can find are 25A or less and none seem able to do an equalize.

[Sunking]

The problem you are running into is there is not a lot of quality chargers for 12 volts. Most of what you see is for automotive. Change your search term to "MARINE BATTERY CHARGERS". Then you will see a lot more options and better quality.

How much money do you want to spend? Xantrex has 12 volt models in 20/40/60 amps with EQ. It is an excellent charge rwith Power Factor Correction so you can operate from any ****y sources like battery inverters generators with crappy regulation and low Power Factor.

If it were me do what I do. Use a variable regulated 12 volt power supply made for ham radio operators. They come in at up to 70 amps. Adjust the voltage to whatever you want up to 15 volts. Astron is one of them and look for any model with VS. Example a VS-20ML. Is a 20 amp supply that not only can you set the voltage, but also Current Limit and full metering. You can charge any battery type up from 2 volts to 15 volts with one. The algorithm will be Constant Current which you can control from 1 to 20 amps, and Constant Voltage which you set from 2 to 15 volts.

[SunEagle]

Iota and Samlex make some nice 3 stage 12v charge controllers.

[Sunking]

Iota and Samlex make some nice 3 stage 12v charge controllers.

Yes they do, but does Iota have EQ? EQ would be a 4th stage.

I think you can buy an option plug for the DLS15 to make it go to 14.7 volts or something like that????

[gardner]

How much money do you want to spend?

Ideally, a couple hundred or less. This is an ultra low-budget setup. The Vector/B&D job that Mike mentioned was going for US$180 or so, which is in the ballpark.

I found some models oriented to the RV market that go for $300 to $400 which is getting spendy for me.

I do have a 30V 10A variable power supply that I can set to 16V and current limit to 8A or something. This would be okay, but not ideal for doing equalization and it would probably not give enough current to do a larger battery bank.

[SunEagle]

Yes they do, but does Iota have EQ? EQ would be a 4th stage.

I think you can buy an option plug for the DLS15 to make it go to 14.7 volts or something like that????

You are correct. The Iota requires the IQ4 plug to get EQ level charging. Their 45amp model with the IQ4 costs about $200.

[Sunking]

I do have a 30V 10A variable power supply that I can set to 16V and current limit to 8A or something. This would be okay, but not ideal for doing equalization.

Actually it is ideal for any battery charging assuming you can set the voltage with some degree of accuracy.

Any battery charger is just a cheap scaled down DC power supply. A good variable bench power supply that you can control both voltage and current will run circles around any battery charger. You can select voltages and currents that ideally match your battery. Battery chargers cannot do that.

Go to Ebay and you can find a lot of Astron Power Supplies. Key in on any that have a model number of VS-XXML. XX = current. A VS-20ML is a 20 amp supply and should be around $80 to $150 new. You can charge any battery from 2 to 15 volts with it. Buy a Hobby charger like they use for RC and the Astron and you can charge any battery chemistry of today and tomorrow up to 36 volts.

[gardner]

I have a Vector VEC1093 Smart Battery Charger [...] and it does EQ .

I was reading the manual online. I see that there is an "equalize" indicator, but the manual doesn't say how to enter equalization setting or what the current/voltage is or any of that. How do you activate equalize?

[Willy T]

I was reading the manual online. I see that there is an "equalize" indicator, but the manual doesn't say how to enter equalization setting or what the current/voltage is or any of that. How do you activate equalize?

It has a hole you stick a tooth pick in or a ball point pen to activate, there are no settings, it's a fixed algorithm.

It's a smart charger, like most of them, it's not designed to charge a battery that has a load on it.

[Sunking]

I see that there is an "equalize" indicator, but the manual doesn't say how to enter equalization setting or what the current/voltage is or any of that. How do you activate equalize?

EQ is a Constant Voltage so there is no current adjustment. Current will taper to ZERO when the battery voltages = Source voltage just like Absorb and Float.

[gardner]

The reading I've done makes me think it's at least a little different than bulk/absorb scenarios.

Rolls recommends C/20 current and run up to 2.58 - 2.67 volts per cell for as long as:

the electrolyte temperature stays under 45C-50C
the electrolyte remains under 1.265 SG
the SG continues to rise hour by hour and
you are patient -- "may take many hours"

http://support.rollsbattery.com/support/solutions/articles/430-corrective-equalization-instructions

Because the batteries are gassing freely at this voltage, there will always be somewhere for the current to go -- into electrolyzing water -- and it won't taper to nearly zero as an absorption charge will. I gather from various sources that the C/20 current limit is just a ballpark to set a maximum gassing rate that you'd get. It is probably self limiting, since the faster its gassing the more of the plates lose contact with the electrolyte.

Automated equalize cycles in chargers that do that, seem to be timed runs at 2.58 VPC for 1-3 hours. Outback stuff, for example, seems to either use 1hr or programmable timing defaulting to 1h. At a guess, the VEC1093 would do something like that. Shame it's not documented.

[Sunking]

The reading I've done makes me think it's at least a little different than bulk/absorb scenarios.

Rolls recommends C/20 current and run up to 2.58 - 2.67 volts per cell for as long as:

the electrolyte temperature stays under 45C-50C
the electrolyte remains under 1.265 SG
the SG continues to rise hour by hour and
you are patient -- "may take many hours"

All the C/20 or .05C means is the charger being used has at least that much current available for charging. Bulk is the only Constant Current mode. Absorb, Float, and EQ are all Constant Voltage. What Rolls is saying is if you have a 100 AH battery, you need at least a charger with a minimum 5 amps to EQ the battery and that is really over kill. You can EQ a 100 AH battery with a 100 amp charger if you want with no real problem if you ramp up the voltage slowly to stay under C/8.

The problem with performing an EQ with solar is there are not enough hours in a day to complete the cycle as it can take up to 24 hours. You apply the EQ charge until the SG quits rising and all cells are equal. That can take 24 hours with 12 being the norm if performed every 30 to 45 days. It takes a generator or commercial power to do that. Not only does the generator and charger need to be large enough to supply a full C/8 charge current, but also supply the load demands while EQ charging is taking place. That is impossible to do with solar?

To go one step further Solar is not really capable of completing the full Adsorb Cycle with a 3-Step process unless you are in long summer months with light loads. To complete a full Absorb cycle a constant voltage is applied until charge current tapers down to .01C-.03C. No solar charge controller has that capability to measure. Instead they do it based on time, and for that to work you have to switch from Bulk which can take a quite a while before switching to Absorb, and by the time that happens, there may or may not be enough daylight to complete the cycle. If not you are under charged.

Trojan and even Rolls have had to change voltage set points for solar systems because of the flood of warranty claims coming in from solar users having sulfated batteries from chronic daily undercharging. 3-Stage charging works great if you use commercial power or a generator because time is of no issue to complete the cycle. Today Trojan has changed what they call Daily Charge for RE users and done away with traditional 3-Stage charging in favor of 2-Stages of Absorb and Float. The standard T-105 no longer has a Bulk setting, just Absorb = 7.4 volts up from 6.9 volts. Float = 6.6 volts down from 6.75 volts, and EQ = 7.75 volts up from 7.5 volts. What this does is forces your Charge Controller to operate as a 2-Stage charger and forcing your controller to stay in Constant Current mode longer so as to charge as fast as possible in the limited amount of time. Basically 7.4 volts is an just short .1 volts short of the old EQ setting with conventional chargers. Rolls has taken upon similar changes.

[gardner]

All the C/20 or .05C means is the charger being used has at least that much current available for charging.

Interesting. I read it as a current limit.

I'm expecting be able to set my bench power supply to C/20 current limit and 2.58 VPC and let 'er rip.